Threading machine for insulator blanks



K. H. WEBER April 18, 1939.

THREADING MACHINE FOR INSULATOR BLANKS Filed Feb. 26, 1937 2 Sheets-Sheet 1 TO SOUECE OF surf/0N lNVENTOR MEL H WEBER ATTORNEYS pril 18, 1939- K. H. WEBER 2,154,793

THREADING MACHINE FOR INSULATOR BLANKS Filed Feb 26, 1937 2 Sheets$heet 2 INVENTOR V KAEL 1 1/5558 20 BY 1 ATTORNEYS Patented Apr. 18, 1939 UNlT STATES THREADING MACHINE FOR, INSULATOR BLANKS 4- Claims.

This invention relates to machines used in the manufacture of spark plug insulators, more particularly to a machine adapted to thread a bore in an insulator blank before the same is fired in a kiln.

In the past, threads have been formed on internal bores of unfired ceramic material such as insulators for use in spark plugs for internal combustion engines, by a manual operation in which the thread cutter is carefully turned into the bore to form the thread and then carefully removed by a reverse rotation of the thread cutter. This operation is costly and slow. The present invention contemplates the provision of a machine which will attain cleaner and more uniform results with greater speed and facility than may be obtained by the manual operation. A machine is contemplated in which both hands of the operator are free to place the blanks in position for the threading operation and to remove the same after the threading operation is complete. The machine is designed to be substantially automatic which will reverse its tool relations in proper sequence within predetermined limits without interference on the part of the operator.

It is, therefore, an object of this invention to provide a machine which will cut a thread or make a similar conformation upon a blank of unfired ceramic material without the necessity of an operator controlling the movements of the actuating elements of the machine, the operator being required to place the blanks into and re move them from operative position in the machine.

It is a further object of this invention to pro vide a machine in which a thread-cutting device is advanced to cutting relation with a work body and after the thread cutting device has advanced a definite distance with relation to the work body, a reversal of rotation isautomatically obtained to withdraw the thread cutter from its operative relation with the work body without placing any strain upon the conformed portions of the work body.

It is a further object of this invention to pro vide a machine in which a working element will advance and retreat with respect to the work body without interference or control by an operator.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economics of manufacture, will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Figure l. is an elevational view, partly in section, of the machine.

Figure 2 is a plan view of the machine.

Figure 3 is an enlarged elevational view, partly in section, showing a detail or" the machine.

Figure i is a plan view taken along the line 4- of Figure 1.

Referring to the drawings, particularly to Figure 1, a base it is provided which has an upstanding boss ii apertured to support in vertical position a column Q? to which the moving portions of the machine are attached as will be described hereinafter.

Adjacent the boss l i, an aperture 53 is provided in the base which is provided with a flanged sleeve it cooperating with the aperture 53 and held in operative relation therewith by any convenient means such as, for example, screws I5. The aperture 63 in the base It is in communication with a source of suction (not shown) by means of a conduit it. The sleeve M is provided at its upper end with an internal resilient collar ll positioned flush with the bore. The resilient collar ll may be formed of soft rubber or the like and is adapted at its upper side to seat a work body W such as, for example an unfired ceramic body shown in the form of a spark plug insulator. The suction in the conduit 56 holds the work body W in position on the collar I! to allow forming operations to be performed thereon as will be described hereinafter.

In the present embodiment of the invention, as illustrated in the drawings, the work body W is to be provided with a threaded aperture in its upper end as shown. The substance of which the work body W is formed is of a soft chalky nature, extremely frangible and very likely to chip or crush under stress when formed into sections of small diameter such as found in screw threads. It is, therefore, necessary for the formation of a clean accurate thread in the aperture of the work body W that the frangible material of which the work body is formed is not subjected to undue stresses which would tend to chip the material. As shown in Figure l, a tap T is provided to form the thread in the bore of the work body W. The tap T is held in operable position by means of a chuck C which is well known in the art and need not be described in detail. The chuck C is mounted for controlled rotation on a vertical shaft it which is held in position by means of bearings 19 to align with the bore in the work body W.

The bearings 18 are mounted upon arms 2f! which are an integral part of a split collar 24 which embraces the column l2. Clamping means 22 are provided to cooperate with the split collar 2| to allow the collar to be fastened in any position on the column i2, the parts being held in alignment and to prevent relative rotation by means of a key 23 which cooperates with cooperating slots in the column l2 and the collar 2|. In this manner, the bearings l9 and the working parts of the machine may be raised or lowered to suit the conditions imposed by the proportions of the work body W. Micrometer adjusting means it are provided to cooperate between the column l2 and the collar 2| so that the aforementioned adjustments may be made with facility. This adjusting means is well known in the art and need not be described in detail.

The split collar 2| is provided on the side diametrically opposed from the bearings [9 with a platform 25 which is supported by suitable brackets 25. A motor M is mounted upon the platform 25 by means of bolts 21; the motor mounting is preferably made adjustable to allow tension of driving belt 3 to be varied which acts between the motor pulley and the driven pulley N. The cooperation between the motor and the moving parts of the machine will be described in detail hereinafter.

The vertical shaft it on which the chuck C is mounted is moved in a vertical line to and from operable relation with the work body W by means of a threaded portion kiA on the shaft, preferably adjacent its upper end to cooperate with a partially threaded sleeve 2?. An outwardly extending flange ETA on the sleeve 21 is adapted to cooperate with the upper side of the] upper bearing [9, and is held in position thereon by any convenient means such as, for example, by screws. The relation between the threaded portion 18A and the sleeve 2! enables the shaft I 8 to move downwardly or upwardly, depending upon the direction of rotation of the shaft I 8. The threaded portion MA is preferably designed to have the same pitch as the thread cutters on the tap T so that when the tap T enters the aperture in the work body W, it will be advanced primarily by the threads MA into the Work body W to allow the formation of a clean-cut thread without placing any strain upon the frangible material of the work body. The strain of advancing the tap T into the aperture of the work body W is borne by the thread collar 21. Then, upon reversal of the shaft 3, the tap will be withdrawn from the aperture in the work body by the interaction of the threads 18A and the sleeve 21. In this manner, the frangible material of the work body W is not exposed to stresses which would tend to crumble it during the period in which the tap T is moving into or out of operable relation.

In order that the shaft I8 may be conveniently rotated in both directions, two faced pulleys 23 are mounted adjacent bearings IS, the pulleys being mounted preferably upon sleeves which journal the shaft H3. The sleeves S may be mounted in any convenient manner in the bearing l9 as, for example, by key K. Ball bearings are preferably used to reduce the friction of rotation of the pulley 28 to a minimum. Each pulley is provided with a hardened plate 28A, held in position by means of screws or the like, which forms one portion of a clutch mechanism adapted to transmit the rotation of either pulley to the shaft IS. The pulleys 28 are rotated in opposite directions by means of a belt system to be described hereinafter.

The clutch member, cooperating with the shaft [8, is in the form of a spool 30 which is provided with gripping faces 3| of any suitable friction material, held in position by means of screws 32. The shaft l8 threads the bore of the spool 3!) and is provided with a projection 33 preferably in the nature of a key to cooperate with a key-way 34 in the bore so that rotation of the spool 30 will be transmitted to the shaft 18. The movement of the spool 30 relative to the shaft I3 is primarily controlled by means of a manual lever L which is provided at its lower end with a bifurcated portion which embraces the spool 38. Each arm of the bifurcated portion is provided with a roller 35, journaled on a pin 36 fixedly held in position in each bifurcated arm. The roller '35 cooperates with the flanges of the spool to control the movements thereof. 0n the side adjacent the column [2, the arms of the bifurcated portion are apertured to journal a stub shaft 31 which is fixedly mounted in plates 38 anchored to the split collar 2| by means of screws 39. Cotter pins are preferably used to hold the shaft 3! in position. The shaft 31 forms a fulcrum about which the manual lever L may be moved to control the movements of the spool 38.

The arms of the bifurcated portion of the manual lever L extend considerably beyond the pin 31 and a yoking portion 4t: is provided to extend therebetween, being held in position by means of screws 4!. Centrally positioned on the yoking portion 46, a boss 32 is provided which is formed with oblique sides to reach-an obtuse apex as is clearly shown in Figure 3. The apex of the oblique sides cooperates with a similarly contoured member 43, which is mounted in a square aperture 44 in the split collar 2|. The member 43 is thrust in the direction of the spool 35 to cooperate with the boss 42 by means of a helical spring 45 which acts between a bore 46 in the member 43 and the seat 46A formed in the collar 2!.

The cooperation between the boss 42 and the member 43 holds the spool 30 in engagement with either of the faced pulleys 28, depending upon which of the oblique sides of the members 42 and 43 cooperate. The manual lever L is available to move the spool 38 from one position to the other as desired. In the illustrations, the spool is shownin a neutral position which is not stable because the apices of the boss 42 and'the member .3 are coincident.

For greater convenience in use for manufacturing process where speed is vital, an automatic reverser is provided which will change the direction of rotation of the shaft I 8 after it has .2

moved within predetermined limits. The direction of rotation, in turn, determines the longitudinal movement of the shaft as pointed out above. In the modification shown, the movement of'the tap T, as controlled by the shaft I8, is the determining factor which controls the limits within which the parts of the machine are to operate. It is, therefore, essential that the shaft I8 is provided with means to control the movements of the spool as. To attain this objective, the

upper end of the shaft I8 is provided with a head [8B which cooperates with a U-shaped member 56. A pivot 5! is provided to allow limited movement of the U-shaped member 5b in cooperating with the upper end of the shaft it, the pivot 5! being mounted in a bracket 52 which may be fastened to the arm 2i! in any convenient manner as, for example, by screws 53.

The lower arm of the U-shaped member is bifurcated and adapted to embrace the shaft 53 and to cooperate with the head 5818 while the shaft I8 is being moved downwardly by its rotation in the threaded sleeve 2?. The upper arm of the U-shaped member 5b is provided with a stud bolt as which is in threaded relation therewith and is locked in position by a nut after a desirable adjustment between the stud bolt 54 and the head liiB of the shaft has been attained. The stud bolt 5% is adapted to cooperate with the head I8B in the upward movement of the shaft 28. The two arms of the U-shaped member as are employed in this manner in establishing limits of movement of the shaft E8 in either upward or downward directions.

Adjacent the pivot 5!, an arm 55 is provided which is integral with the U-shaped member so and is apertured to receive a stirrup 56 by means of a pin threading aligning holes. A second stirrup 5'! is pivoted on pin WA on the manual lever L at a point adjacent the spool 33 and is adapted to cooperate with the upper stirrup 56 through an adjustable connecting rod 538. A U-shaped spring 59 is provided between the stirrup 5E and the connecting rod 53 to absorb shocks due to the inertia of the moving parts. 1

The cooperation between the head 18B of the shaft is, the stud bolt and the lower bifurcated arm of the member 59 gives a control mechanism, which at predetermined times thrusts the member 56 about the pivot ii! to move the arm 55 in an upwardly or downwardly direction. The movement of the arm 55 is transmitted to the stirrup 56, then to the U -shaped spring 59 which, in turn, transmits it to the connecting rod 58, then to the stirrup 5'? which, through the medium of the pivot 57A, moves the manual arm L to accord with the movement of the arm 55. The head 18A, moving within the limits prescribed by the stud bolt 56 and the lower bifurcated arm of the member 58, is empowered by this mechanism to move the spool 3d into gripping relation with either of the faced pulleys 28.

As shown in Figures 1 and 3, the spool 39 is shown in a neutral position between the faced pulleys 28 with the apices of the members 2 and 43 adjacent each other, which, as pointed out before, is not a stable condition inasmuch as the helical spring 36 urges the member ll-3 outwardly tending to force the member L from the neutral position and place the spool 33 in gripping relation with either the upper or the lower faced pulley 2B. The oblique faces of the members 42 and 43, in cooperating with each other, form a means for maintaining the spool in driving relation with the pulleys which, as pointed out before, are being rotated in opposite directions.

Referring to Figures 2, there is shown a motor arrangement which is convenient for driving the faced pulleys 28 in opposite directions. For this purpose, a stud 6B is provided which is fitted into the brackets 25 to project laterally to form a journal for two pulleys N and 6! which are preferably made integral. The pulley N has been described before as cooperating with the motor M, being driven by a belt B. In order to get a proper speed reduction from the motor M, the pulley N is preferably made of considerable diameter so that the pulley ill, which is of a definite diameter determined by the distance between the faced pulleys 23, may be driven at a proper speed. A second pulley 66A is mounted on an adjustable stud which may be moved by means of an adjusting bolt Y for belt-tightening purposes on the opposite side of the bracket 26 on which the stud so is mounted. The pulley GIA is of the same diameter as the pulley BI and cooperates therewith by means of a driving belt V which cooperates with the V notch of both pulleys. The arrangement of the belt V is best shown in Figure 1 in which the pulleys 6| and 61A cooperate with the vertical bights while the horizontal nights are in cooperation with the pulleys 28. In this way, one belt cooperates with four pulleys, the driver pulley 5! which cooperates with the large speed-reducing pulley N, the upper and lower faced pulleys 28 and the idler pulley BIA. In this manner, the upper and lower pulleys 28, which are a portion of the reversing apparatus, are driven in opposite directions so that the spool 38 may cooperate with either of them to attain the desirable direction of rotation.

In the operation of the machine, the frangible work body W is first placed in position by the hand of the operator on the seat formed by the resilient collar El, the Work body being held there by the action of the suction. The drawings illustrate an unfired ceramic insulator blank for a spark plug as a work body which is made of brittle chalk-like material unsuitable to carry any stresses such as found in thread cutting operations. A central bore is provided in the work body in which, in this case, a thread is to be cut by the tap T of proper dimension. The machine is then adjusted to give the tap T the proper travel in both upward and downward directions by adjusting the various devices supplied for this purpose such as, for example, the adjustable device Z l for the split collar 2|, which adjusts the limit of downward travel of the tap T and the adjustable stud bolt 54 cooperating with the head HEB which controls the limit of upward travel of the tap T.

After the machine has been adjusted with relation to the work body W so that both the lower and upper limits of travel are established for giving a proper length of thread in the bore of the work body, and at the same time will give sufficient clearance to allow convenient insertion and removal of the work body from the resilient collar ii, the motor M is started which immediately begins driving the belt 13 to move in turn the belt V which drives the pulleys 28. By means of the manual lever L, the spool 30 may be shifted to contact either of the pulleys 28 to rotate the shaft l8 and the tap T in the proper direction, which, in turn, through the interaction of the threaded portion lSA and the partially threaded sleeve 21, causes the shaft to move upwardly or downwardly.

Assuming that the position of the tap T is such that it is preferable to move the shaft l8 upwardly, this movement normally is attained by having the manual lever L in its upper position so that the spool 3b is contacting the upper pulley 28, which is rotating in a proper direction to cause the desired movement of the shaft IS. The manual lever L, through the action of the members 42 and 43, will stay in its upward position until the head IBB contacts the stud bolt 54 and moves the member 50 about the pivot 5|.

This movement displaces the arm 55 which tends to thrust the connecting rod 58 downwardly and eventually will cause the lever L to be shifted past the neutral point as determined by the coincidence of the apices of the members 42 and 43 and so cause the manual lever L to shift to its lower position, where it will be held by the other oblique sides of the members 42 and 43 to cause a driving contact between the spool 30 and the lower faced pulley 28. The lower faced pulley 28, in the meantime, has been rotating in the opposite direction from the upper faced pulley 28 andwill cause a reverse of rotation of the shaft l8. This reversal will, by its action with the partially threaded sleeve 21, cause the tap T to move downwardly into operable relation with the work body W. The operator has placed the work body W in operable position upon the suctional holding means provided in the base member I while the tap T was adjacent its highest point of travel. The parts of the mechanism will remain in this position until the shaft l8 has been advanced downwardly to a position where the under side of the head I813 will cooperate with the bifurcated lower arm of the U- shaped member 59.

Before this condition is obtained, the tap T has engaged the bore of the work body W, and has penetrated a suificient distance to conform the bore with the proper threads. When a sulficient depth of thread has been attained, the cooperative relation between the head itB, as pointed out above, will be attained so that the lever 55 is again displaced to pull the manual lever L upwardly through the medium of the connecting rod 58. When the manual lever L has again been shifted to the up position, the

rotation of the shaft [8 will again be reversed by having the spool 30 again engage the upper faced pulley 28 which causes the tap T to be backed or withdrawn from the aperture in the Work body W.

As pointed out before, the pitch of the threads IBA is the same as the pitch of the thread cutter T so that no strain will result upon the frangible material of the work body W. In this manner, it is possible to advance the tap T into the Work body W to out a thread and after the cutting operation is complete, upon reversal of rotation, it can again be withdrawn without causing stresses which will tend to crumble the frangible material.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of 1. In a device of the class described, holder means adapted to cooperate with a work body, spindle means adapted to move in a line with the work body to advance and withdraw a work member to and from the work body, a pair of plates cooperating with the spindle means and rotating in opposite directions, means cooperating with the spindle means and the plates to reverse the rotation of the spindle means, holding means cooperating with the means to reverse the rotation of the spindle means to hold the same in a predetermined cooperative position with one of the plates, automatic means to release the holding means and to shift the means to reverse rotation of the spindle means into cooperation with the other plate.

2. In a device of the class .described, holder means adapted to cooperate with a work body, spindle means adapted to move in line with the work. body to advance and withdraw a work member with reference to the work body, spool-like means to rotate the spindle means, a pair of positively rotating plates cooperating with a spocl-lil e means to reverse the rotation of the spindle means by selective contact with the spoollike means, automatic means to control the plates selectively to reverse the rotation of the spindle means after the spindle has performed predetermined functions and manual means to overcontrol the automatic means and determine the rotation of the spindle means both for direction of rotation and speed of rotation.

3. In a device of the class described, holder means adapted to maintain a work body in a predetermined position and to prevent rotation.

thereof, spindle means to control a threading tool to move the threading tool in a predetermined line with the work body, means on the spindle to advance and withdraw the threading tool having substantially the same rate of advance as the pitch of the threading tool, a pair of plates cooperating with the spindle means and adapted to rotate in opposite directions, control means cooperating with the spindle means and selectively with the plates to control the rotation of the spindle means, and automatic means to cooperate with the control means to reverse the rotation of the spindle means after the threading tool has moved between predetermined limits.

4.111 a device of the class described, fixed holder means to maintain a work body in a predetermined fixed position, a threading tool cooperating with the work body and adapted to form threads thereon, spindle means cooperating with the threading tool and adapted to move in a predetermined line with reference to the work body, a pair of plates adapted for rotation in opposite directions, control means cooperating with the spindle and selectively with either one of the pair of plates to control the direction of rotation of the spindle, a second control means cooperating with the spindle to advance and to withdraw the threading tool in substantially the same rate as the pitch of the threading tool, and automatic means cooperating with the first control means to reverse the rotation of the spindle after the tool has moved between predetermined limits.

KARL H. WEBER. 

